Fluorinated polymers with pendant side chains containing ion exchange groups in the form such as sulfonic acid are known in the prior art. These resins are particularly useful where it is necessary to have thermal and chemical stability, e.g., for use as a membrane or a diaphragm in an electrolytic chlor-alkali cell. Suitable disclosures of ion exchange polymers are set forth in U.S. Pat. Nos. 3,773,634 and 3,793,163 wherein films are employed in a chlor-alkali cell for formation of chlorine and caustic. A teaching of use of an ion exchange polymer in a porous diaphragm for formation of chlorine and caustic is disclosed in U.S. Pat. No. 3,775,272.